This disclosure pertains to scannable wireless receivers generally that may scan different frequency bands, such as amplitude modulation (AM) and frequency modulation (FM) bands. Without limitation, the background is described in connection with FM receivers, but it should be understood that the disclosure pertains to other frequency bands as well. FM is popular in many developed countries and is growing in popularity in a number of developing countries. In the United States and Europe, FM broadcast stations use a bandwidth of 200 KHz assigned to them at different frequencies or positions within the 87.5 MHz to 108 MHz range. In Japan the FM band or available frequency spectrum is a 76 MHz to 90 MHz band. There, an FM channel can be centered at multiples of 50 KHz, with a frequency spacing of at least 200 KHz between any two valid stations. The FM center frequency can be centered at multiples of 50 KHz in some parts of the world and at multiples of 100 KHz in other parts of the world. Hence, scanning for FM bands at multiples of 50 KHz or multiples of 100 KHz are two useful operations. With the growing popularity of FM transmission all over the world, low-cost integrated FM receivers have become important to integrate into mobile handsets like cell phones and Internet devices as well as FM-supporting integrated circuits of various types for those and other products.
A radio receiver typically has a tuner with provisions for automatically searching across the frequency band and selecting the frequency of a transmitting station. Such a radio receiver may be integrated into a mobile device, such as a mobile phone, car, boat, plane, etc., and is of particular advantage in that it may provide for selection of broadcasting stations with a minimum distraction to the user of the mobile device for greater safety.
In cases using a FM radio application on a mobile device, the user expects FM channels to be ready when the user enters or launches the FM application. In mobile devices, when the user turns on the device and launches the radio application (or starts the ignition of a car, for example) with an available FM antenna, it is beneficial to keep the system updated with available FM channels even before the user initiates a scan. Typical FM search procedures are based on multiple algorithms such as Signal to Interference Noise ratio (SINR), for example, and the stations found in the search can vary based on the variable SINR including the position of the mobile device. Therefore, the user might need to keep scanning or searching again and again when the mobile device location changes. For example, a user at home might find very few channels when compared to open air like on a terrace of the home. Similarly in a car, when a user is in a city, the user can find more channels when compared to being in a rural environment. Thus, the valid FM channel list is dependent on the location of the phone/car and must be manually updated by the user, creating a problem.
What is needed is a device and process for maintaining a valid FM channel list that may be updated dynamically without customer intervention based on changes in the device location and the availability of an antenna. For example, a device capable of performing a background low power search that builds a close hysteresis and initiates a new search based on the geographic location. This search should run based on the state of the FM radio and available geographic location changes making sure the FM radio channels are updated in the background based on the geographic location with no user intervention required.
Accordingly, there is a need for systems, apparatus, and methods that overcome the deficiencies of conventional approaches including the methods, system and apparatus provided hereby.